Zn Alloy Sheets Research Articles

Natural and Artificial Aging Effects on the Deformation Behaviors of Al-Mg-Zn Alloy Sheets.

This study investigated the effects of aging profiles on the precipitate formation and the corresponding strengthening and deformation behaviors of Al-Mg-Zn alloys. The alloys subjected to natural aging (NA) demonstrated significantly enhanced ductility at equivalent stress levels compared to those subjected to artificial aging (AA). In AA-treated alloys, η' and η-phases with incoherent interfaces were formed, while GP zones and solute clusters were dominantly exhibited in the NA-treated alloy with a coherent interface with the matrix. Due to the change in interface bonding, the dislocation movement and pinning behavior after deformation are varied depending on the aging conditions of Al-Mg-Zn alloy sheet. Thus, the elongation to fracture of the NA alloy sheet was improved compared to that of the AA alloy sheet because of the enhanced work-hardening capacity and the thin precipitate-free zone (PFZ). Deformation textures and dislocation densities varied between NA and AA treatments, as revealed by electron backscatter diffraction (EBSD) and kernel average misorientation (KAM) analysis. The interactions between the precipitates, dislocations, and the PFZ in the AA- and NA-treated alloys were analyzed via transmission electron microscopy (TEM). The insights gained from this research provide a valuable foundation for industrial applications, particularly in sectors demanding lightweight, high-strength materials, where optimizing the aging process can lead to significant performance improvement and cost savings.

Development of Mg–6Al–4Sn–1Zn alloy sheets with ultra-high strength by combining extrusion and high-speed rolling

Achievement of ultra-high yield strength of above 400 MPa for rare-earth-free magnesium (Mg) alloys is quite difficult via traditional thermal-mechanical processing. In this study, Mg–6Al–4Sn–1Zn alloy (ATZ641) sheet with the yield strength of 410 MPa, ultimate tensile strength of 442 MPa, and elongation of 5.1 %, was fabricated by combining extrusion and high-speed rolling (HSR). The results showed significant refinement in the grains of high-speed rolled ATZ641 alloy due to dynamic recrystallization (DRX) effectively promoted by particle-stimulated nucleation (PSN) of pre-existing relatively coarse Mg17Al12 precipitates uniformly distributed along grain boundaries, formed during extrusion prior to HSR. Meanwhile, the Mg17Al12 nano-precipitates with high number density, mainly due to dynamic precipitation during HSR and submicron Mg2Sn precipitates formed during both extrusion and HSR, suppress DRX and thus promote the formation of a certain amount of subgrains via particle pinning. The excellent mechanical properties are mainly attributed to fine-grain strengthening, high density residual dislocations and presence of numerous hybrid particles such as bimodal size (micron and nanometer) Mg17Al12 precipitates and submicron Mg2Sn precipitates as well as a large amount of subgrains. This study offers an important notion for developing rare-earth-free Mg alloys with ultra-high strength.

Enhanced formability of Al–Mg–Si–Zn alloy sheet via dislocation structure and texture during cold rolling

The effects of cold rolling deformation on microstructure, texture, and formability of Al–Mg–Si–Zn alloy were systematically investigated using OM, SEM, TEM, XRD, and tensile tests. The results indicated that the effect of cold rolling deformation on the recrystallized microstructure and texture of the sheets mainly depended on the differences in dislocation structure and texture distribution. With the increase of cold rolling deformation, the dislocation structure gradually changed from a mixture of density dislocation walls and microbands to a lamellar bands structure, the large-angle boundary gradually increased, and the size of dislocation cells gradually decreased, which indicated a gradual increase of the stored deformation energy. In addition, the deformation texture increased gradually with the raise of cold rolling deformation. After T4P treatment, the recrystallized grain size gradually reduced with the increase of cold rolling deformation. The main recrystallization textures in the sheets with 41 % and 55 % deformation were Cube {001}<100> and CubeRD {310}<001> textures, respectively. The CubeND {001}<310> texture was predominantly present in the sheets with 69 % and 82 % deformation, meanwhile some P {011}<233> texture was also observed in the sheets with 82 % deformation. It was found that the dislocation structure and deformation texture distribution formed in the sheet with 82 % cold rolling deformation contributed to smaller recrystallized grains and weaker P texture after solution heat treatment, which enhanced the average plastic strain ratio r value and improved the formability.

Effect of transverse gradient extrusion process on texture and mechanical properties of Mg–3Al–1Zn alloy sheets

Transverse gradient extrusion (TGE) processes with different die inclined angles of 15°, 30°, 45°and 60° were used to produce Mg–3Al–1Zn sheets, thereby tailoring texture and mechanical properties of Mg alloy sheets. Microstructure, deformation texture and final mechanical properties of the obtained sheets were detected and discussed. Furthermore, the rheological behavior of Mg alloys during extrusion was analyzed by finite element method. As the TGE die inclined angle changed, the flow velocity along the transverse direction (TD) and effective strain difference along extrusion direction (ED) were changed during extrusion, and therefore the microstructure and texture of extruded sheets are altered. With increase of TGE die inclined angles, fine grain size and uniform microstructure were obtained. The base poles of most grains for the extruded sheets gradually deviate from normal direction (ND) to ED at center region and inclined from ED to TD at 1/4 edge region. A large elongation of 33.9 % and a low yield stress of 125 MPa can be obtained in the TGE-45 sheet.

Improved mechanical properties of Mg−3Al−1Zn alloy sheets with TD-preferred texture prepared via turned bearing extrusion

To improve the ductility and formability of the Mg−3Al−1Zn alloy sheets, novel turned bearing extrusion (TBE) dies are designed based on the conventional extrusion (CE) die. Finite element simulations are performed to catch the distributions of strains and temperature fields during extrusion. The results show that gradient distribution of strain along the normal direction (ND) in TBE dies leads to the gradient microstructure. Furthermore, the transversal direction (TD)-preferred texture with ND-oriented grains deflecting toward extrusion direction (ED) is achieved. The TD-preferred texture is generated by the more activated non-basal slips in the TBE due to the higher temperature at a higher strain than that in the CE die. Because of the texture modification, the ductility and bendability of the TBE sheets. The elongation of the TBE-6 sheet reaches 33% and the bending angle reaches 83.5° when the sample is tested along 45° direction.

Understanding the superior mechanical properties of Mg–3Al–Zn alloy sheets: Role of multi-type unique textures

Understanding the superior mechanical properties of Mg–3Al–Zn alloy sheets: Role of multi-type unique textures

Comparison of edge crack behavior of Mg sheets prepared by online heating rolling

Low-alloying and low-cost magnesium alloy sheets have the potential for large-scale application. Therefore, the edge cracking developed during the rolling is of great importance. In this work, Mg-1.0Mn-0.5Al (MA10), Mg–2Zn-1.5Mn (ZM21), and Mg-3.0Al-1.0Zn (AZ31) alloy sheets were rolled at 150 °C in different single-pass reductions using online heating rolling. Their edge cracking behaviors at the edge of rolled sheets after large strain rolling were investigated and compared through the scanning electron microscope (SEM), electron backscatter diffraction (EBSD), and digital image correlation (DIC) technique. The results show that compared with ZM21 and AZ31 rolled sheets, MA10 rolled sheets exhibit the most severe edge cracking behavior after large strain rolling. This is mainly attributed to the lower recrystallization degree and ultimate compressive strength, as well as higher strain localization during the plastic deformation. Meanwhile, both coarser second phase particles at the edge and larger grain size difference also promote the initiation and propagation of edge crack in MA10 alloy rolled sheets. In addition, the small crack is developed in front of the crack tip in all of Mg alloys rolled sheets after a single-pass reduction of 75% due to the stress concentration at triple junctions caused by large rolling reduction and maximum shear stress along the plane collinear with the major crack.

Development of corrosion-resistant Mg-Al-Ca-Mn-Zn alloy sheet with good tensile properties and stretch formability

To develop high-performance magnesium alloy sheets for sheet applications in the automotive industry, we investigated the effects of the Al content on the tensile properties, stretch formability, and corrosion resistances of Mg-xAl-0.5Ca-0.4Mn-0.8Zn (mass%, x = 2, 5, 8, AXMZx101) alloy sheets. The addition of 5% Al led to the highest limiting dome height of 6.4 mm. The AXMZ5101 alloy sheet also exhibited a good combination of in-plane isotropic strength and ductility. The 0.2% proof stress and elongation to failure were 193 MPa and 24.2% for the rolling direction and 188 MPa and 23.1% for the transverse direction, respectively. Such moderate Al addition resulted in a significantly improved corrosion resistance with a corrosion rate of 0.18 mm/y after immersion in a 3.5% NaCl solution for 7 days, which was approximately 1/4 lower than that of a commercial Mg-Al-Zn alloy sheet. An in-depth characterization revealed that such a good combination of tensile properties and stretch formability is associated with the small grain size, weak basal texture, high work hardenability, and activation of nonbasal slips and that a high corrosion resistance should be achieved by the formation of a dense oxide-rich layer.

Study on Bulk Texture and Mechanical Properties of As-Extruded Wide Mg-Al-Zn Alloy Sheets with Different Al Addition.

The wide Mg alloy sheets produced by hot extrusion usually can easily form an inhomogeneous texture, resulting in anisotropic mechanical properties and poor formability. However, few studies have been carried out on the bulk texture investigation at different areas of as-extruded Mg alloy sheets, especially the Mg alloys with different alloying elements. In this work, the effect of Al on the bulk texture and mechanical properties at different areas for three wide Mg-Al-Zn alloy sheets with different Al contents (Mg-3Al-0.5Zn, Mg-8Al-0.5Zn and Mg-9Al-0.5Zn) are mainly investigated by neutron diffraction. The results showed that a strong and uneven basal texture was formed in the Mg-3Al-0.5Zn sheet. Meanwhile, the intensity of the basal texture was significantly weakened due to the numerous fine precipitates of Mg17Al12 particles, with the Al content increasing, which hinder the grain growth during extrusion, while fine recrystallized grains have a more random orientation. The enhanced tensile properties in Mg-8Al-0.5Zn and Mg-9Al-0.5Zn alloy sheets are ascribed to the cooperation effect of a refined microstructure, precipitates and weakened basal texture. Among the three Mg alloy sheets, the Mg-8Al-0.5Zn alloy sheet has a yield strength of about 270 MPa, an ultimate tensile strength of about 330 MPa and ultimate elongation of about 16% in the extrusion direction, which possesses the most excellent comprehensive mechanical properties.

Tailoring microstructure and texture of Mg–3Al–1Zn alloy sheets through curve extrusion process for achieving low planar anisotropy

• Symmetric curve extrusion (SCE) and asymmetric curve extrusion (ACE) processes were firstly proposed to fabricate AZ31 Mg alloy sheets. • The SCE and ACE sheets exhibited unique textures which were ascribed to the introduction of additional flow velocity difference along transverse direction during extrusion. • The ACE sheet exhibited the lowest basal pole intensity because of the introduction of extra asymmetric shear deformation during ACE process. Curve extrusion processes, including symmetric curve extrusion (SCE) and asymmetric curve extrusion (ACE) processes, were proposed to fabricate Mg–3Al–1Zn (AZ31) alloy sheets with the aim of improving planar anisotropy. For comparison, traditional extrusion (TE) was conducted on producing AZ31 sheets. The dynamic recrystallization and flow behavior of AZ31 Mg alloy during extrusion were examined and analyzed, and the final microstructures and mechanical properties of AZ31 sheets were investigated. In comparison with the TE sheet, finer grain size, more uniform microstructure and weaker tilted basal texture were achieved in the SCE and ACE sheets. Both the SCE and ACE sheets exhibited unique textures which basal poles tilted to extrusion direction (ED) and new transverse direction (TD)-tilted texture component was developed. The reasons were mainly ascribed to the introduction of additional flow velocity difference along TD during extrusion. Furthermore, the ACE sheet exhibited the lowest basal pole intensity, which was attributed to the introduction of extra asymmetric shear deformation during extrusion process. As a result, the ACE sheet showed the lowest yield strength and r -value, but highest elongation and n -value. Improving the planar anisotropy of AZ31 sheet was achieved by the ACE process.

Forming novel texture and enhancing the formability in Mg–3Al–Zn alloy sheets fabricated by transverse gradient extrusion

Transverse gradient extrusion (TGE) process was firstly proposed to fabricate Mg–3Al–1Zn (AZ31) alloy sheet, thereby tailoring the strong basal texture of conventional extruded (CE) sheet. A novel texture formed in the TGE sheet, which tilted about 65° from normal direction (ND) to extrusion direction (ED) and elongated along transverse direction (TD). The basal texture component disappeared completely. Because of the formation of unique texture and uniform fined grain structure by TGE process, the extruded sheet exhibited a large Erichsen value (IE) of 6.7 mm at room temperature, which was approximately 258% of the CE sheet.

Microtexture-induced anomalous anisotropic tensile behavior in Mg–Al–Zn alloy sheet

An anomalous in-plane anisotropy was found in a basal-textured Mg–Al–Zn alloy sheet due to a minor fraction of transverse direction (TD)-orient (0001) poles induced high activation of tensile twinning. This led to deteriorated tensile properties along the TD, emphasizing an importance of microtexture designing for wrought magnesium with high-performance.

Effect of microstructural heterogeneity on the balanced-biaxial and tensile behavior of a Zn alloy sheet

A 0.65 mm thick Zn sheet was processed at room temperature by equal channel angular sheet extrusion (ECASE), which allowed for the fabrication of a heterogeneous material. The processed sheet's heterogeneity manifested as larger dislocation clusters and smaller grain sizes on the surface than in the sheet's center, generating as well a 35% increase in yield strength while preserving a fracture elongation of 26%. ECASE processing resulted in a slightly higher deformation limit than that of the as-received material with a weight reduction of 9%. The improvement in the processed sheet's mechanical properties was associated with the formation of twins on the surface, resulting in a smaller grain size and heterogeneity between the twins-free and twinned grains. These two microstructures produced a combination of hard and soft zones. ECASE processing formed twins in particular grains that in turn created a high density of geometrically necessary dislocation (GND) arrays in twin-free neighboring grains. It should be noted that the twinned grains had a low density of geometrically necessary dislocations (GND). In addition to the heterogeneity between twinned and twin free grains, a heterogeneous GND distribution was formed between the surface and the processed sheet's center, with the basal slip system dominating.

Microstructure Analysis and Bulk Texture Study in Wide Magnesium Alloy Sheets Processed by Twin-Roll Casting

The wide magnesium (Mg) alloy sheets produced by twin-roll casting (TRC) are prone to have an inhomogeneous microstructure and basal texture. Texture has a significant effect on the properties of Mg alloy sheets for the processes after TRC, which can be greatly modified by alloy composition. However, systematic studies on the bulk texture of TRCed Mg alloy sheets using neutron diffraction are lacking. In this study, neutron diffraction was used to explore the bulk textures in different positions of the Mg, Mg–Al–Zn, and Mg–Al–Sn–Zn alloy sheets produced by TRC, besides microstructure and micro-texture analysis using field emission scanning electron microscopy and electron backscattering diffraction. The influence of alloy composition on the microstructure and texture evolution of TRCed Mg alloy sheets is explored and discussed. The TRCed pure Mg sheet possesses a relatively strong basal texture, and the texture distribution is inhomogeneous; while TRCed Mg–Al–Sn–Zn alloy sheets feature much weaker textures and a relatively homogenous distribution in different positions. The present study provides guidance for the control of texture via tailoring alloy compositions, which provides candidate Mg alloys suitable for the TRC process.

Evolution of recrystallization texture for Cu-30% Zn alloy sheets with high Young’s modulus in the transverse direction

Miniaturization of electric connecters with higher stability in the coupling force is demanded as components of electric vehicles. Copper alloys are attractive materials from the perspective of electric conductivity. It is considered that Brass orientations {110}<112> has high Young’s modulus along the transverse direction (TD) since the Young’s moduli of copper single crystals show a maximum value at the <111> direction. The authors could successfully develop the near-Brass orientation in TD of the annealed sheets by performing additional warm rolling at a low reduction in thickness for cold rolled Cu-30% Zn alloy (brass) sheets with material cost lower than pure copper. The near-Brass recrystallization texture with a main component {110}<223> showed maximum orientation density after annealing at 723 K when warm rolling was performed at 623 K. In addition, we discussed the mechanism of the recrystallization texture evolution for Cu-30% Zn alloy sheets, which were subjected to the combined rolling consisting of cold and warm rolling using a conventional rolling mill and subsequently annealed at 723 K, in view of annealing twinning in the early stage of recrystallization.

冷間圧延後に温間圧延を施したCu–30％Zn合金板の再結晶集合組織とヤング率

冷間圧延後に温間圧延を施したCu–30％Zn合金板の再結晶集合組織とヤング率

Effects of Deformation Texture and Grain Size on Corrosion Behavior of Mg–3Al–1Zn Alloy Sheets

Effects of deformation texture and grain size on mechanical properties and corrosion behavior of the Mg–3Al–1Zn (AZ31) alloys were systematically investigated. The results revealed that the ultimate tensile strength (UTS) and fracture elongation (FE) significantly increased from 232 to 273 MPa and 12.5 to 26.4%, respectively. According to the immersion and electrochemical measurements, the results indicated that the corrosion resistance of the alloy was improved obviously. Via electron backscattered diffraction (EBSD), corrosion morphology showed that the propagation of local pitting corrosion was suppressed, which is ascribed to grain refinement, higher texture intensity, and lower dislocation density after rolling and subsequent annealing.

Enhancement of Corrosion Resistance and Discharge Performance of Mg–5Li–3Al–1Zn Sheet for Mg-air Battery via Rolling

The corrosion behavior at open circuit potential (OCP) and the discharge performance under impressed anodic current of Mg–5Li–3Al–1Zn (LAZ531) alloy sheets with different rolling reductions are investigated using hydrogen evolution, potentiodynamic polarization, electrochemical impedance spectroscopy, and galvanostatic discharge measurements. The results show that rolling increases the corrosion resistance and strengthens the discharge ability of LAZ531 alloy, which is attributed to the increased density of twins and the change of grain orientation. Of those, the LAZ531 alloy with 20% rolling reduction (LAZ531%-20%) has high and steady discharge voltage at small current density for long time, with the values of 1.490 V at 2.5 mA cm−2 and 1.411 V at 10 mA cm−2. The grain boundaries and twins play the same roles on the corrosion and discharge processes, which are attacked preferentially than the grain interiors and accelerate the dissolution of LAZ531 alloy.

Effect of shear deformation on plasticity, recrystallization mechanism and texture evolution of Mg–3Al–1Zn alloy sheet: Experiment and coupled finite element-VPSC simulation

Microstructure characterization and texture evolution of multi-passes isothermal symmetry and asymmetry rolling, or namely differential speed rolling (DSR), of Mg–3Al–1Zn alloy sheets were systematically investigated at different temperatures and strain levels. Also, two scale model coupling finite element and a visco-plastic self-consistent model (FE-VPSC) was employed. Results indicate that the predominant dynamic recrystallization (DRX) mechanism transits from twinning DRX at 150 °C to continuous DRX at 250 °C attributed to the distinctively activated deformation modes. It was found that shear deformation induced in DSR plays a crucial role on the activation of deformation modes and related DRX mechanisms. Based on the calculation of effective Schmid factor (ESF), shear deformation is believed to promote the activation of contraction twinning and pyramidal <c+a> slip by increasing their ESFs. Furthermore, the concentration of grain orientations caused by profuse operation of basal <a> slip can facilitate the activation of twinning and pyramidal <c+a> slip during DSR. As a result, twinning DRX dominated region was obviously enlarged owing to a larger fraction of twinning at low temperature (<200 °C). Meanwhile, profuse activation of pyramidal <c+a> slip at high temperature (>200 °C) can accelerate the continuous DRX. After annealing at 250 °C for 1 h, fine grains with an average size of 3.36 μm and a large basal titled angle (∼26°) were attained for the twinning DRX controlled sheet at 150 °C.

Influence of Nd or Ca addition on the dislocation activity and texture changes of Mg–Zn alloy sheets under uniaxial tensile loading

In situ hard X-ray diffraction experiments were carried out to investigate the dislocation slip activity of Mg-1 wt.% Zn-based alloys containing Nd or Ca during tensile loading. Diffraction patterns collected during tensile loading at 3 temperatures were analyzed using a convolutional multiple whole profile fitting procedure. High activation of nonbasal <a> and pyramidal <c+a> dislocations was found in the Nd- and Ca-containing alloys. The microstructure evolution after 10% deformation was examined by complementary EBSD measurements. The microstructure evolution was related to the differences in the initial texture and active deformation modes, according to the alloying and temperature. In-grain misorientation axes analysis obtained from the EBSD measurements confirms that the addition of Nd or Ca contributes to the higher activity of prismatic <a> slip. The high activity of prismatic <a> slip leads to a broadening of the basal poles perpendicular to the loading direction and a strengthening of the <101‾0> pole along the loading direction. The overall dislocation density evolution at elevated temperatures is controlled by dynamic recovery and dynamic recrystallization. These thermally activated mechanisms are retarded in the Nd- or Ca-containing alloys.